Various conventional and tissue Doppler echocardiographic indexes were compared with pressure-volume loop analysis to assess their accuracy in detecting left ventricular (LV) diastolic dysfunction in patients with heart failure with normal ejection fraction (HFNEF). Diastolic dysfunction was confirmed by pressure-volume loop analysis obtained by conductance catheter in 43 patients (19 men) with HFNEF. Their Doppler indexes were compared with those of 12 control patients without heart failure symptoms and with normal ejection fraction. Invasively measured indexes for diastolic relaxation (tau, dP/dt(min)), LV end-diastolic pressure, and LV end-diastolic pressure-volume relationship (stiffness, b dP/dV, and stiffness constant, beta) were correlated with several conventional mitral flow and tissue Doppler imaging indexes. Conventional Doppler indexes correlated moderately with the degree of LV relaxation index, tau (E/A: r=-0.36, P=0.013; isovolumic relaxation time: r=0.31, P=0.040) and b (deceleration time: r=0.39, P=0.012) but not with beta, in contrast to the tissue Doppler imaging indexes E'/A'(lateral) (r=-0.37, P=0.008) and E/E'(lateral) (r=0.53, P<0.001). Diastolic dysfunction was detected in 70% of the HFNEF patients by mitral flow Doppler but in 81% and 86% by E'/A'(lateral), and E/E'(lateral), respectively. Of all echocardiographic parameters investigated, the LV filling index E/E'(lateral) was identified as the best index to detect diastolic dysfunction in HFNEF in which the diagnosis of diastolic dysfunction was confirmed by conductance catheter analysis. We recommend its use as an essential tool for noninvasive diagnostics of diastolic function in patients with HFNEF.